Tension scale system for lifting cable of a telescoping boom crane

ABSTRACT

A crane having a telescoping boom which is extendable and contractable to various lengths, which boom has a cable trained thereover for lifting a load. A tension scale system is provided for the cable of the telescoping boom, which system includes a tension dynamometer located on the stationary or base boom section; the lifting cable is connected to a winch, and then extends along the boom and through a reeving system located on the outermost section of the boom; the cable is then trained over a pulley rotatably mounted on the outermost boom section and the cable is then dead-ended on the base section of the boom by being connected directly to the tension dynamometer on the base section. An electrical connection extends from the tension dynamometer directed to the operator&#39;&#39;s cab so that the load on the cable may be read directly by the operator in the cab of the crane.

Unite States Patent [191 Johnston TENSION SCALE SYSTEM FOR LIFTING CABLE OF A TELESCOPING BOOM CRANE Inventor:

[73] Assignee: Harnischfeger Corp., Milwaukee,

Wis.

Roger L. Johnston, Marion, Iowa [22] Filed: Apr. 24, 1972 [21] Appl. No.: 246,893

[52] US. Cl. 212/55, 340/267 C [51] Int. Cl. B66c 23/06 [58] Field of Search 212/39 R, 39 B, 39 OB,

212/39 MS, 39 A, 39 P, 55; 340/267 C, 73/141, 143; 324/144 [56] References Cited FOREIGN PATENTS OR APPLICATIONS 118,292 U.S.S.R 340/267 C Primary ExaminerEvon C. Blunk Assistant Examiner-Hadd Lane Att0rneyJames E. Nilles [57] ABSTRACT A crane having a telescoping boom which is extendable and contractable to various lengths, which boom has a cable trained thereover for lifting a load. A tension scale system is provided for the cable of the telescoping boom, which system includes a tension dynamometer located on the stationary or base boom section; the lifting cable is connected to a winch, and then extends along the boom and through a reeving system located on the outermost section of the boom; the cable is then trained over a pulley rotatably mounted on the outermost boom section and the cable is then dead-ended on the base section of the boom by being connected directly to the tension dynamometer on the base section. An electrical connection extends from the tension dynamometer directed to the operators cab so that the load on the cable may be read directly by the operator in the cab of the crane.

2 Claims, 4 Drawing Figures PMENIEB Ill" 1 3 I973 SHEET 2 OF 2 TENSION SCALE SYSTEM FOR LIFTING CABLE OF A TELESCOPING BOOM CRANE BACKGROUND OF THE INVENTION Prior art load weighing systems for telescoping booms of cranes have previously utilized different 'arrangements. One example of such a prior system was to use a pulley or sheave on the outer boom section with a sheave opposite to the normal straight line path of the cable so that a component load of the true tension in the cable was converted and read by a tension read-out device which held the said pulley opposite to the normal straightness of the cable.

Another type of prior art system was to install the tension dynamometer or other device on the outermost or fly section of the telescoping boom and between the vertical portion of the load carrying cable and the normal cable becket on the boom head. This type of system was disadvantageous on telescoping booms because it required a wind up drum for an electrical cable or required other means to extend and retract the electric cable or other transferring means for read-out 'in the operators cab. This electric cable wind up drum or take up device for the electric wire was costly and often got in the way of other component parts of the boom, especially when the latter was fully extended.

SUMMARY OF THE INVENTION The present invention provides a lifting cable tension scale system for a telescoping boom of a crane and in which a tension dynamometer is located on the base or non-extending section of the telescoping boom. The lifting cable is trained over the telescoping sections of the boom and around the outermost end of the fly or end boom section, and is furthermore then reeved between the outer end of the end boom section and a block andpul ley device to which the load is attached. The cable then is trained over a separate pulley located on the outer end of the fly or outer boom section and th end of the cable is then connected or dead-ended to the tension dynamometer located on the base boom section. An electrical wire of fixed length can then be mounted on the base section of the boom and connects the tension dynamometer on the end of the base sec-' tion of the boom with an electric read-out scale in the operators cab of the crane.

With the tension scale system of the present invention wind-up drums or other take up devices for the electrical wire between the dynamometer and the cab are eliminated; there is no need for an extendible electric wire between the base section and the fly or outer section of the boom as required by prior art devices.

The arrangement of the present invention is such that the load may be weighed directly by the tension dynamometer on the end of the base boom section or the reading may be made by the operator directly in the operator's cab. t

The system provided by the present invention substantially reduces the cost of prior art tension systems by reducing the number of parts required, such as wind up drums or other take up devices.

These and other objects and advantages of the present invention will appear hereinafter as this disclosure progresses, reference being had to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a side elevational view of a truck crane having a telescoping boom and embodying the present invention, certain parts being shown in phantom lines;

FIG. 2 is an enlarged, fragmentary view of a portion of the crane shown in FIG. 1;

FIG. 3 is an elevational view of a portion of the telescoping boom shown in FIG. 1, but when the latter has 0 been extended, and furthermore showing certain parts as being broken away or removed for the sake of clarity, the view being on an enlarged scale from that shown in FIG. 1; and

FIG. 4 is a view taken along line 44 in FIG. 3, but on an enlarged scale, and showing the tension dynamometer;

DESCRIPTION OF A PREFERRED EMBODIMENT The mobile truck crane shown in FIG. 1 and which embodies the present invention includes a vehicle V having ground engaging, rubber tired wheels 1, and a power plant, such as an internal combustion engine E. A support member in the form of a revolvable upper 4 is mounted on a slewing ring 5 and is rotatable relative to the platform 6 of the vehicle. A telescoping boom B is pivotally mounted at 7 to the revolvable upper 4 so that it can be swung about a horizontal axis 7 between a lower position shown and a vertically raised position (not shown) in the known manner. A hydraulic cylinder unit 9 is connected at 10 to the revolvable upper and at 11 to the boom for vertically positioning the boom B.

An operators station is provided in the form of a cab 14 on the revolvable upper 4 and in which the operator is located for operating the boom. The boom includes a base or non-extending section 20, a second section 21 a third section 23 and a fly or outer boom section 24. Sections 21-24 are all telescopingly mounted for contraction to the position shown in FIG. 1 or extension relative to one another as shown in FIG. 3, by bydraulic cylinder means or other devices (not shown) which are usually located within the boom sections.

The outer boom section 24 has a pulley 30 rotatably mounted in the head 31 of the end section, and a wide reeving pulley 32 is also rotatably mounted in the head 31. A lifting block 34 has a load engaging hook 35 and a wide reeving pulley 36 mounted thereon. The block 34 is thus connected with the head 31 of the outer boom section by the reeving of the cable around reeving pulley 32 on the outer boom section and the reeving pulley 36 rotatably mounted in the block 34. The load cable C is wound around the lifting winch W at the rear end of the boom section 20 and this cable then extends over the upper side of boom sections 21, 23 and 24, is trained around pulley 30, and is then reeved around the wide reeving pulley 32 and 36 in the known manner, as for example having 12 loops or lines of reeving between the pulleys 32 and 36. An idler pulley 40 is mounted by a bracket 41 on the inner and generally lower end of the head 31 of the outer boom section 24 and the cable C after passing around the reeving pulley 36 then passes over the idler pulley 40 located on the boom end section 24. The end of the cable C has a clevis 42 fixed thereto and this clevis is attached to a plunger 44 of a tension dynamometer TD. The tension dynamometer is pivotally connected at 46 to a bracket 47 which is rigidly fixed to the base boom section 20. The tension dynamometer itself is of conventional construction and includes a visible scale 49 for direct reading of the tension of the cable C. Generally speaking, these tension dynamometers are of the type which can read to 40,000 lbs. and for example, the tension in the cable itself may be only in the neighborhood of 16,000 lbs. depending of course on the load, these figures are given by way of example only.

An electric wire 50 is connected to the tension dynamometer and is fastened alongside the boom base section 20 and then extends to the operators cab 14 where it passes through the operators cab wall at 51 to the interior of the cab. Located within the interior of the cab is an electric read-out device 54 for the tension dynamometer TD for reading the load as measured by the tension dynamometer. This read-out device is of the conventional type and may be a scale such as a face dial with a conventional needle. A pair of wires 55 and 58 extend from the read out device 54, one of the wires 55 connected to a circuit breaker 56 which in tun is connected to a source of electric power (now shown) by means of a wire 57. The other wire 58 extends from the readout device to a ground 59.

By means of the present invention, the pulley 40 is located on the outer, fly section of the boom and as the boom is extended to the position shown in FIG. 3, the cable is paidout along the underside of the boom sections. The electrical wire 50 however is a fixed length and is mounted on the base or stationary boom section 20 and therefore requires no wind-up drums or other take up devices as required by other prior art devices. lnead the hoisting or load cable C is dead-ended on the non-telescoping base section as by being connected to the tension dynamometer located on the base section.

I claim:

1. A crane including a support member, an operators station on said member, a boom including a plurality of telescoping boom sections including a non-extendible base section pivotally mounted at one end on said support member and having a free end, said boom also having a telescoping outer boom section, a winch adjacent the boom, a load cable connected at one end with said winch for being wound thereon, said outer boom section having a head and a pulley reeving means including an upper pulley mounted on said head and around which said cable is trained for supporting the load, said outer boom section also having an idler pulley rotatably mounted on its said head and adjacent a lower side thereof and over which idler pulley said cable is passed, a tension dynamometer fixed on said free end of said boom base section, the other end of said cable being operatively connected to said dynamometer, said reeving member including a lifting block suspended from said load cable and located between said upper pulley and said idler pulley, a read-out device located adjacent said operators station, an elongated connection located on and fixed along the length of said boom base section, said connection being connected between said dynamometer and said read-out device whereby the tension of said load cable is measured by said dynamometer and is indicated so that it can be read at said readout device by the operator in said station.

2. The crane as set forth in claim 1 further characterized in that said elongated connection is an electric wire and said read-out device is an electrical read-out device. 

1. A crane including a support member, an operator''s station on said member, a boom including a plurality of telescoping boom sections including a non-extendible base section pivotally mounted at one end on said support member and having a free end, said boom also having a telescoping outer boom section, a winch adjacent the boom, a load cable connected at one end with said winch for being wound thereon, said outer boom section having a head and a pulley reeving means including an upper pulley mounted on said head and around which said cable is trained for supporting the load, said outer boom section also having an idler pulley rotatably mounted on its said head and adjacent a lower side thereof and over which idler pulley said cable is passed, a tension dynamometer fixed on said free end of said boom base section, the other end of said cable being operatively connected to said dynamometer, said reeving member including a lifting block suspended from said load cable and located between said upper pulley and said idler pulley, a read-out device located adjacent said operator''s station, an elongated connection located on and fixed along the length of said boom base section, said connection being connected between said dynamometer and said read-out device whereby the tension of said load cable is measured by said dynamometer and is indicated so that it can be read at said readout device by the operator in said station.
 2. The crane as set forth in claim 1 further characterized in that said elongated connection is an electric wire and said read-out device is an electrical read-out device. 